• Boudewijn T H M Sleutjes, Inger Montfoort, Pieter A van Doorn, Gerhard H Visser, and Joleen H Blok.
• Department of Clinical Neurophysiology, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands.
• J. Neurol. Neurosurg. Psychiatr. 2015 Nov 1;86(11):1234-9.

ObjectiveTo determine and compare the diagnostic accuracy of electrically elicited multiplet discharges (MDs) and fasciculation potentials (FPs) in motor neuron disease (MND).MethodsPatients were eligible when they had MND in their differential diagnosis and were referred for electromyogram (EMG). Stimulated high-density surface EMG of the thenar muscles was performed on the same day as standard EMG examination. High-density recordings were analysed for presence of MDs and needle EMG of any muscle investigated in the cervical region for presence of FPs.ResultsOf the 61 patients enrolled in this diagnostic study, 24 patients were clinically diagnosed with amyotrophic lateral sclerosis (ALS) and 11 patients with progressive muscular atrophy (PMA). Another diagnosis was made in 26 patients. Sixteen patients in whom MDs were detected were diagnosed with either ALS (n = 11) or PMA (n = 5; sensitivity = 47.1%, PPV = 94.1%). MDs were detected in only one patient initially diagnosed with PMA, but in whom later on, multifocal motor neuropathy could not be excluded (specificity = 96.2%). Electrically elicited MDs had a higher specificity than FPs (96.2% vs 53.9%, p < 0.001, n = 26) and lower sensitivity (47.1% vs 85.3%, p = 0.002, n = 34). When considering presence of MDs in MND as neurogenic EMG abnormality, lower motor neuron involvement of ≥ 1 EMG region increased from 50% to 73.5% (p = 0.008, n = 34).ConclusionsElectrically evoked MDs are highly specific for ALS and PMA and are an early sign of lower motor neuron dysfunction.Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

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